Study On The Synthesis And Micellar Behaviors Of PNIPAM-b-PPAPEA Block Copolymers

In this thesis,the block copolymer poly[N-isopropyl acrylamide]-b-poly[2-(4-phenylazophenoxy)ethyl acrylate](PNIPAM-b-PPAPEA)was synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization,using N-isopropyl acrylamide(NIPAM)and 2-(4-phenylazophenoxy)ethyl acrylate(PAPEA)as monomers,2-cyanoprop-2-yl dithiobenzoate(CPDB)as a chain transfer agent,2,2'-azo-isobutyronitrile(AIBN)as initiator.Then,PNIPAM-b-PPAPEA was assembled into micelles in water.The structure and micellar behavior of the block copolymers were characterized and tested.The main research contents are as follows:Firstly,2-cyanoprop-2-yl dithiobenzoate(CPDB)was synthesized by the consecutive reaction of Grignard reagent formed from the reaction of bromobenzene and magnesium powder with hydrochloric acid and 2,2'-azo-bisisobutyronitrile(AIBN).Then 2-(4-Phenylazophenoxy)ethyl acrylate(PAPEA)was synthesized by the consecutive reaction of 4-hydroxy azobenzene with 2-chloroethanol and acryloyl chloride.Poly[2-(4-Phenyl-azophenoxy)ethyl acrylate](PPAPEA)was prepared via the RAFT polymerization of PAPEA,using CPDB as a chain transfer agent and AIBN as initiator.The effects of reaction time,the concentration of initiator and chain transfer agent on the polymerization of PAPEA were investigated.The resulting PAPEA and PPAPEA were characterized by FT-IR,1H-NMR,and GPC.And,the photoresponsive behavior of PPAPEA was determined by UV.The results showed that the kinetic curve of the polymerization of PAPEA revealed good linear relationship,and the molecular weight distributions were narrower(<1.3).When the molecular weight of PPAPEA increase,the rate of isomerization became slow under ultraviolet irradiation and the recovery of photo-induced PPAPEA was a little change under natural light.Secondly,PNIPAM was prepared via the RAFT polymerization of NIP AM,using CPDB as a chain transfer agent,AIBN as initiator and N,N-Dimethyl formamide(DMF)as solvent.PNIPAM-b-PPAPEA block copolymer was synthesized by RAFT polymerization using PNIPAM as a macromolecular chain transfer agent,PAPEA as monomer and AIBN as initiator.And the effects of the polymerization reaction kinetics were investiged.The resulting PPAPEA and PNIPAM-b-PPAPEA were characterized by FT-IR,1H-NMR,and GPC.The results showed that the kinetic curve of the polymerization of PAPEA reveals good linear relationship;the molecular weight of PNIPAM-b-PPAPEA increases with the increasing conversion of PAPEA and the molecular weight distributions were narrower(<1.3).Thirdly,the PNIPAM-b-PPAPEA block copolymer was dissolved in DMF,then the PNIPAM-b-PPAPEA micellar solution was prepared by dialysis againse water,the photoresponsive behavior of the micelle solution,the size and the morphology of micelles were investigated by UV-spectrophotometer,3D Dynamic Light Scattering(DLS)and transmission electron microscope(TEM),respectively.The results show that the morphology of PNIPAM-b-PPAPEA micelles is spherical,the particle size increased with the increasing of molecular weight;the micelle solution exhibited good photoresponsiveness;the particle size decreases with the increasing the temperature.